1. Field of the Invention
The invention relates to a display module and a light guide device.
2. Description of Related Art
In the display region of a display device, various types of spatial light modulators are applied to convert an illumination beam into an image beam, for example, transmissive liquid crystal display (LCD) panels, liquid-crystal-on-silicon (LCOS) panels, or digital micro-mirror devices (DMDs). The light efficiency of a transmissive LCD panel is less than that of a LCOS panel, and the cost of a DMD is greater than that of a LCOS panel.
Generally, in a projector using the LCOS panel, an s-polarized beam is reflected by a polarizing beam splitter (PBS) to the LCOS panel. Then, the LCOS panel modulates the s-polarized beam into a polarized beam with other polarization states, and reflects the polarized beam to the PBS. The PBS filters the polarized beam into an image beam, which is then transmitted to an image-forming lens. Finally, the image-forming lens projects the image beam onto a screen to form an image on the screen or forms a virtual image in the air or on any other virtual image plane.
In the projector using the LCOS panel, the beam splitting plane of the PBS is inclined with respect to the LCOS panel by about 45 degrees, so that the PBS occupies a large space between the LCOS panel and the image-forming lens. As a result, the distance between the image-forming lens and the LCOS panel is long, so that the projector is thick and bulky.